Origin is 157 years old this month. (Probably) the most famous book in science was published on 24 November 1859. To celebrate we have uploaded hundreds of new images of letters, bringing the total number you can look at here to over 9000 representing more than 2000 letters, written both before and after the book appeared. You can now see examples of letters to Darwin from nearly 250 different people, and letters he wrote to 150 more.

Darwin played an important role in the controversy over vivisection that broke out in late 1874. Public debate was sparked when the Royal Society for the Prevention of Cruelty to Animals brought an unsuccessful prosecution against a French physiologist who had performed vivisection on dogs.

Darwin was a photography enthusiast. This is evident not only in his use of photography for the study of Expression and Emotions in Man and Animal, but can be witnessed in his many photographic portraits and in the extensive portrait correspondence that Darwin undertook throughout his lifetime. His close friend and botanist Joseph Dalton Hooker would come to call Darwin’s epistolary exchange of photographic images as his “carte correspondence”.

For all his working life, Darwin used letters as a way both of discussing ideas and gathering the ‘great quantities of facts’ that he used in developing and supporting his theories. They form a fascinating collection from many hundreds of correspondents, containing diagrams and drawings, personal observations, photographs, and even specimens.

Read and search the full texts of more than 8,500 of Charles Darwin’s letters, and ﬁnd information on 6,500 more. Discover complete transcripts of all known letters Darwin wrote and received up to the year 1871.